clk: qcom: check for change in RCG configuration during set_rate

For DSI byte clock RCG, check if there is a change in existing
settings before updating RCG configuration. This is needed to
avoid glitch on the display panel when there is a change in the
DSI byte clock frequency with display enabled.

Change-Id: I8ef0331cbb466b399cd12199b4d335ed44997dbc
Signed-off-by: Padmanabhan Komanduru <pkomandu@codeaurora.org>